The present invention relates to a ratchet mechanism for the headband of a protective helmet or similar headgear, a mechanism that allows for adjustment of the size and fit of the headband.
Protective helmets are commonly worn in the industrial workplace to prevent or reduce the likelihood of head injuries. The hard hat is the most common and well-recognized protective helmet. A hard hat consists of three primary components—a shell, a headband, and a suspension system—which cooperate to reduce the potential for injury by attenuating some translational energy of the force of an impact to the helmet.
With respect to the construction and protection afforded by a hard hat, the American National Standards Institute (“ANSI”) promulgates minimum performance requirements for protective helmets and further classifies helmets based on their ability to reduce the forces of impact and penetration, as well as their ability to protect against high voltage electric shock. See, for example, ANSI Z89.1-1997 (R1998), American National Standard for Industrial Head Protection.
As mentioned above, a hard hat or similar protective helmet is comprised primarily of: a shell, a headband, and a suspension system. These primary hard hat components cooperate to provide the requisite level of protection. The hard hat shell itself causes any force of impact to be spread across the surface area of the shell. The hard hat suspension separates the wearer's head from the shell such that there is an air gap between the shell and the wearer's head that provides for further attenuation of the force of an impact to the shell. Specifically, when an object strikes the shell of the hard hat, the shell itself flexes inward and the straps of the suspension system will stretch. The air gap accommodates the flexing of the shell and stretching of the straps, but, under normal conditions, prevents the wearer's head from contacting the hard hat shell.
Of course, for a hard hat to provide the appropriate level of protection, it must fit snugly on the wearer's head. In this regard, it is common for the headband of a hard hat to be adjustable to provide for such a snug fit. In this regard, a headband typically has one of two common sizing mechanisms, a pin-lock arrangement or a ratchet mechanism. Regardless of the chosen sizing mechanism, the headband is commonly a flexible, one-piece member that has overlapping rear end portions. With a pin-lock mechanism, a first of the rear end portions of the headband is provided with a pin, and the second of the rear end portions is provided with series of holes at spaced intervals. As such, the pin of the first rear end portion can be inserted through one of the holes of the second rear end portion, thus forming a loop of a selected circumference to fit snugly around the wearer's head. With a ratchet mechanism, lateral movement of the overlapping rear end portions of the headband is effectuated through a rack and pinion arrangement or similar gear arrangement.
As one example of a ratchet mechanism, reference is made to U.S. Pat. No. 4,888,831 issued to Oleson, a patent that is incorporated herein by this reference. As described in the '831 patent, a preferred ratchet mechanism is often a rack and pinion arrangement which operates within elongated overlapping slots defined by the rear end portions of the headband, each of said slots defining a series of teeth of a rack gear. The rack and pinion arrangement and the overlapping rear end portions of the headband are housed between a pair of adjoining arc-shaped housing sections which generally conform to the contour of the wearer's head. The rear end portions of the headband are seated for slidable, lateral movement within the arc-shaped housing sections.
Referring still to the '831 patent, and specifically FIG. 3, one preferred rack and pinion arrangement includes five components: (1) an adjusting knob; (2) a first sprocket that is operably secured to the adjusting knob and engages mating gear teeth defined by the outer housing section, the rearward facing of the two housing sections that enclose the headband; (3) a second sprocket that is operably secured to the first sprocket and engages the teeth of the rack gears of the overlapping rear end portions of the headband; (4) a plate or washer interposed between the first and second sprockets; and (5) a spring or similar biasing member interposed between the first sprocket and the plate so as to bias the first sprocket into engagement with the mating gear teeth defined by the outer housing section. The adjusting knob, first sprocket, and the second sprocket all turn together, with clockwise rotation of the adjusting knob tightening the headband, and counterclockwise rotation of the adjusting knob loosening the headband. The interposed plate and spring bias the first sprocket into engagement with the mating gear teeth defined by the outer housing section so that the rear end portions of the headband do not slide or move without appropriate action by the wearer. In other words, since the interposed plate and spring bias the first sprocket into engagement with the mating gear teeth defined by the outer housing section, the position of the rear end portions of the headband is locked absent manipulation of the adjustment knob by the wearer.
For another example of a rack and pinion arrangement, reference is made to U.S. Pat. No. 5,950,245 issued to Binduga. Again, the headband has overlapping rear end portions. Elongated slots are defined by the rear end portions of the headband, with each of said slots defining a series of teeth of a rack gear. As described in the '245 patent with reference to FIGS. 1 and 2, the rack and pinion arrangement preferably includes (1) an adjustment knob with a first end section for providing a grip member suitable for gripping and turning by the wearer and a second end section that is a generally circular cog, the circular cog engaging the teeth of the rack gears defined by the overlapping rear end portions of the headband; (2) a spring assembly integral with or otherwise secured to the adjustment knob; (3) a housing having outer and inner arc-shaped sections that collectively define an internal cavity; and (4) a ring gear assembly fixed within the housing that cooperates with the spring assembly to provide resistance to rotation of adjustment knob. Thus, in practice, rotation of the adjustment knob causes lateral movement of the overlapping rear end portions of the headband relative to one another. However, because the spring assembly has at least one spring tooth projecting radially and adapted for mating with radially projecting teeth of the ring gear assembly, the position of the rear end portions of the headband is essentially locked absent manipulation of the adjustment knob by the wearer.
For yet another example of a rack and pinion arrangement, reference is made to U.S. patent application Ser. No. 10/899,467, now U.S. Pat. No. 7,000,262, which has been incorporated herein by reference. Again, the rack and pinion arrangement and the overlapping rear end portions of the headband are housed between a pair of adjoining arc-shaped housing sections which generally conform to the contour of the wearer's head. The rear end portions of the headband are seated for slidable, lateral movement within the arc-shaped housing sections, again in response to the rotation of an adjustment knob. Furthermore, as described in U.S. patent application Ser. No. 10/899,467, now U.S. Pat. No. 7,000,262, the arc-shaped housing sections have an inherent flexibility that provides for better fit of the headband and increased comfort to the wearer.
However, the rack and pinion arrangements described in the prior art are generally comprised of a number of individual parts, requiring labor-intensive assembly and also increasing the risk of imprecise or flawed operation of the rack and pinion arrangement. For example, the adjustment knob and pinion (also referred to as a sprocket or cog in some of the prior art references) are often separate parts that are assembled together after the shaft of the adjustment knob is passed through the outer housing section. Alternatively, as described in the above-referenced '245 patent, if the adjustment knob and pinion are a unitary part, the outer housing section must be comprised of multiple parts to allow assembly of the components of the rack and pinion arrangement.
Accordingly, U.S. patent application Ser. No. 10/930,633, now U.S. Pat. No. 7,043,772, which has also been incorporated herein by reference, describes a ratchet mechanism for the headband of a protective helmet or other headgear that minimizes the number of components while ensuring precise, reliable operation of the rack and pinion arrangement of the ratchet mechanism. Specifically, the ratchet mechanism also includes a rotational element, which in this case is a unitary body that includes an adjustment knob portion which is positioned on an exterior side of the outer housing section, and a pinion portion which is positioned on an interior side of the outer housing section and within the internal cavity defined by the housing. This rotational element therefore may be characterized as having a unitary construction. In any event, the pinion is adapted to mate with and engage the respective rack gears of the overlapping rear end portions of the headband such that rotation of the pinion causes lateral movement of the overlapping rear end portions with respect to one another.
However, there is a remaining problem associated with such ratchet mechanisms. In high-temperature environments, such as when the protective helmet is part of a firefighter's helmet, the ratchet mechanism may not perform as intended due to warping of the plastic components. Accordingly, there is a need for a ratchet mechanism that can properly function in high-temperature environments while still allowing for ready adjustment of the size and fit of the headband.